There's a lot of noise being kicked up about Brass. Walsh's heavily publicised past, involving benders on "the beak and the booze", helps. As, apparently, do this first-time author's biographical details - such as dropping her first E before her first period or kiss, and working as a "fixer" hooking up male punters with transvestite prostitutes in Barcelona.

And there's no denying that her coming-of-age novel is less a cry from the heart than a bellow from the guts. It is a very noisy piece of writing indeed, not so much executed as spewed by a woman who is, without a shadow of a doubt, a force of nature. She will knock you sideways; whether that makes her a writer is a different matter.

Brass offers us the alternating perspectives of 19-year-old Millie O'Reilly, an English student at Liverpool Uni where her dad is a sociology lecturer, and 28-year-old Jamie Keely, "big brother and fun buddy". He's about to blow seven years of freewheeling by marrying Anne-Marie, a deadly-dull model-cum-nail-artist. Despite this dual narrative, it's the voice, or rather the force of character, of Millie that surges through. "She saw life in the purest terms, la - that you don't put nothing off, you do it now."

Scouse slang for a female prostitute, Brass reads like the diary of a young woman exorcising her demons. Surprisingly, given the youth of its protagonist, it is in many ways an elegy. It is about Millie falling out of love with her behaviour, failing to recognise herself in mirrors, losing her best friend, detesting her sore-infested genitals and, in the last count, being betrayed by her father. "It reads thoughtless and selfish. Superficial. Careless. But it reads true. At least it reads true..." says Millie of a note she writes to her dad. Brass is about clearing off the muck and getting to the point where a voice can emerge.

Walsh lurches between Scouse slang and analogies you've heard before: "I climb out and the cold slaps my bare legs like a wet towel." Millie watches a documentary on spontaneous combustion, involving "bodies melted down to the pelvis, lying forlorn in doorways". More than once, these emotionally blunted, drug-fuelled characters made me think of dismembered dummies from the Chapman brothers - when I had the space to think. Millie makes the reader feel like a speeding passenger snatching a swooshed blur of Liverpool's "manic-depressive" skies. Her splurge is akin to those slow-take flash photos of nightlife, blurred images yellow-striating against the dark. You get the mood, but miss the detail.

One area not short on detail is the sex. The loudest aspect of Brass, its in-yer-face aggression, offers unabashedly ballsy girl-on-girl and girl-on-boy action. Picture the Larry Clark movie Kids (though what gets passed on is the clap and an outbreak of genital herpes, rather than HIV) scripted by Irvine Welsh, with the graphic detail of The Sexual Life of Catherine M and the unleashed fury of Virginie Despentes in Baise-Moi, all centrifuged in a spiral of self-destructive chemically altered bingeing and you're starting to get there. Not pretty, is it?

There are times when you wonder if you've got the belly or prurience to carry on reading. Particularly when Millie rapes-with-consent (if such an act can exist) a girl with, of all things, a lisp, whose back is already black and blue from her father's abuse. In a disabled toilet, Suey, having heaved her innards, whimpers: "Pleathe don't thtop that. Pleathe." "She's letting me do this to her," insists Millie.

So are we being offered a sick mind or a radical pornographer here? (In either event we've been here before - Despentes and French female compatriots were serving up graphically aggressive, if more reactionary, female sexuality back in the early 90s.) "I reduced girls to bodies or bits of. I saw them in terms of tits, legs and arse. I undressed every girl that I met, bending them like Plasticine - this way and that way into every possible position. No one escaped appraisal or categorisation... I saw myself as... some sex-crazed genderless freak."

The daring of her gaze is key to Millie's liberation. Looking around her, at girls on a night out, she ventures: "I doubt any of them have fucked for the sheer love of it. That's the whole tragedy of growing up. It's the one period in your life where there's so much pleasure up for grabs and no one's going to give you too hard a time for reaching out and seizing it."

It's this fearless ownership of pleasure, heading into the realisation that adult emotions lie on the other side of an artificial adolescence fuelled by consumerism, that turns the last quarter of Brass into a page-turner. It all begins to make sense. That Millie first noticed women the day her mother walked out on her life. That the real betrayal was by her father, not her mother. That there is room for love and redemption. And perhaps for Walsh to begin writing, not shouting, a second novel.